The dentate gyrus (DG) is a subregion of the mammalian hippocampus, known to be critical in operating 'pattern separation’, one of the key functions of the hippocampus. There have been considerable theories and hypotheses regarding the function of the DG in learning and memory. In this perspective article, we compare leading theories of DG function. We note that these theories all critically rely on the generation of 'distinct patterns' of neural activity in the DG to represent differences between experiences and reduce interference between memories, a process known as 'pattern separation’. However, these theories are divided by the roles they attribute to the DG during learning and recall, as well as the contributions of specific inputs or cell types within the DG. These differences significantly impact the type and quality of information that the DG transmits to downstream structures in the hippocampus. We work towards a holistic view of the role of the DG in learning and memory by first developing three critical questions to encourage a discussion between the leading theories. We then evaluate the extent to which previous studies address our questions, highlight remaining areas of conflict, and suggest future experiments to bridge these theories.